From what I understand, if we say '100%', we can mean one of two things:

1. 100% of all shaders (and other GPU pipeline components) are filled with data and instructions to process that data

2. the shaders are running at 100% of their maximum clockspeed.

I've been referring to #2 because I imagine some games are structured to only use a certain amount of shaders at the time, BUT the GPU itself is in control of what clockspeed it wants to run at.

when I run real temp and look at GPU utilization, what exactly is it reporting back to me?

With that clarification I can give you a better answer. The graphic card drivers get the card to boost frequencies to 100% when it is required and it likely should be during all gaming. I am not familiar with the program you are using, but if you download and run MSI afterburner it will visually show you the answer to all you gpu related questions (it will show frequencies, usage, fan speed, VRAM use, etc and track them over time).